The present invention generally relates to mechanisms which can control access by personnel into and out of buildings or restricted areas. Specifically this invention is to a new and automated door latch actuator that can interface with a more T-type dead latch of a type typically used in commercial applications. This invention can be provided as originally equipment or as a retrofit on existing doors. The invention is also directed to methods of automatically actuating dead latches.
This invention is directed to improvements to U.S. Pat. No. 5,474,342 issued Dec. 12, 1995 to Smith et al and to U.S. Pat. No. 6,022,056 issued Feb. 8, 2000 to Cope et al. Each of these patents was directed to operate with North American cylindrical dead latches (also sometimes called tubular or bored dead latches). When used with the North American cylindrical dead latch, the apparatus shown in the ""342 Patent and the ""056 Patent serve to release the door when electric signal is applied to it.
Where the conventional door latch assembly in the door is of the North American cylindrical dead latch type, the disclosure shown in the ""342 Patent has an actuator element disposed in proximity to the distal ends of both the spring latch bolt and the dead latch bolt pin. The driver moves an actuator element between first and second actuator positions. When in the first actuator position, the actuator element is operative to retain the dead bolt latch pin in a disabled (retracted) state while allowing the spring latch bolt to extend into the latch/bolt cavity. The actuator element, when moved from the first actuator position, first releases the dead latch bolt pin which moves into the enabled (extended) state and afterward attacks the distal end of the spring latch bolt to move the spring latch bolt from the extended state to the retracted state.
The ""056 Patent was an improvement over the several embodiments of the door latch actuator shown in the ""342 Patent. Particularly, the door latch actuator in the ""056 Patent employs a spring latch plunger and a dead latch plunger mounted in a housing that has latch cavities sized to receive the spring latch bolt and the dead latch bolt pin. The spring latch plunger engages and retracts under pressure of the spring latch bolt, and the dead latch plunger engages the dead latch bolt pin. A drive operates the plungers to first withdraw the dead latch plunger to allow the dead latch bolt pin to move to an enabling position for the spring latch bolt. Next, the drive advances the spring latch plunger and thereby the spring latch bolt is moved to release position, and the door may be opened. The drive in the ""056 Patent is preferably a rotary drive using a motor driven crank and pin system. Sensors are provided to detect the position of the system.
A second type of latch is widely used, especially in commercial application, that significantly differs from the North American cylindrical dead latch. This type of dead latch is common referred to as a xe2x80x9cmortise-typexe2x80x9d dead latch. The mortise dead latch typically is robust and more costly than a cylindrical dead latch and, as noted, finds it is used almost entirely in commercial and industrial buildings. Assemblies shown in the ""056 Patent employ small plungers that confront one another to operate spring latch and the dead latch which, in the cylindrical dead latch are directly adjacent one another. While the disclosure of the ""342 Patent shows several embodiments, including an embodiment using two independently acting solenoids, the technology shown in these patents is difficult to directly apply to mortise-type dead latches. The main difficulty in adapting the technology inherent in the above cited patents derives from the position of the dead latch pin (also called the dead latch trigger) in relation to the spring latch. In the case of mortise-type latches, the dead latch pin is not adjacent to the spring latch but is rather above or below the spring latch depending upon the manufacturer. The wide variety of dead latch pin positions that exist in mortise latches poses a problem for efficient development of an automated door latch actuator. The direct application of the technology in the above described patents would necessitate a different door latch actuator for each different model of mortise dead latch in order to suit the varying positions of the dead latch pin. This increases manufacturing and inventory costs for both manufacturers and distributors.
While the technologies disclosed in the ""342 Patent and the ""056 Patent present significant advances over prior art automated security latch system, further development is indicated for door latch actuators for mortise-type dead latches. There is a need for door latch actuator constructions and methods which will operate mortise-type dead latch assemblies. There is a further need for a mortise-type dead latch automated actuator which can accommodate different mortise-type dead latch constructions thereby to reduce manufacturing and inventory costs. The present invention is directed to those needs.
It is an object of the present invention to provide a new and useful method and apparatus for automated actuating of mortise-type dead latch.
Another object of the present invention is to provide a door latch actuator and method that can be implemented with a variety of differently configured mortise-type lock assemblies.
A further object of the present invention is to provide a door latch actuator that is easily installed into existing door frames to interface with mortise-type dead latches.
Still a further object of the present invention is to provide a door latch actuator that is rugged yet simple in construction.
Still a further object of the present invention is to provide a door latch actuator which is relatively inexpensive in manufacture yet reliable in use.
In its broad form, the door latch actuator of the present invention is adapted to mount in a frame portion of a door and engage a mortise-type dead latch disposed on an edge portion of the door. Typically the mortise-type dead latch includes a spring latch and a dead latch pin or trigger that is linearly spaced-apart from the spring latch along the edge portion of the door. This spring latch is reciprocally moveable between an engaged position so that it can engage the door thereby to retain the door in a fastened state and a release position wherein the door is released from the fastened state. The dead latch pin is reciprocally moveable between enabled position that permits movement of the latch spring from the engaged position to the release position and a disabled position that prohibits movement of the spring latch from the engaged position to the release position. The spring latch is resiliently biased into an engaged position and the dead latch is resiliently biased into the enabled position.
The present invention thus includes a housing having a cavity with a forwardly disposed opening that is sized and adapted to receive the spring latch and the dead latch pin when the door is in the fastened state. A spring plunger is mounted for linear reciprocal movement in a longitudinal throw direction in the housing between an extended position and a retracted position. A dead latch plunger is also mounted for linear reciprocal movement in the longitudinal throw direction in the housing between an advanced position and a withdrawn position. A portion of the spring latch is selectively positionable at a selected first location in the opening of the cavity. This first portion of the spring latch plunger is operative to engage the spring latch bolt when the door is in the fastened state thereby to accommodate different locations of the spring latch on the edge portion of the door. A striker assembly is supported on the dead latch plunger and includes an assemble of strike elements operative to define a strike surface for the dead latch pin. The striker assembly provides a portal for the spring latch at a selected portal location. The strike elements are selectively arrangeable into different configurations thereby to vary the selective portal location to accommodate different spring latch and dead latch pin arrangements. A drive is operable to reciprocally drive the dead latch plunger from the advanced position to the withdrawn position and to advance the spring latch plunger from the retracted position to the extended position. With greater detail, the spring latch plunger is configured as a flat first plate oriented in a first plane that extends longitudinally relative to the longitudinal throw direction so as to have a leading edge. The first portion of the spring latched plunger is defined by an attack head disposed on the leading edge of the first plate. This attack head is slideably mounted on the leading edge of the first plate. Here, the leading edge includes a dovetail structure extending therealong, and the attack head has a dovetail channel formed therein that is sized and adapted to matably engage with the dovetail structure for sliding movement along the leading edge of the first plate. A shield may be provided that is adjustably and selectively mounted to the housing and that is operative to support the attack head during reciprocal movement or the spring latch plunger. The attack head is according configured as a rectangular plate oriented transversely to the longitudinal throw direction. The spring latch plunger is biased into the extended position at a force that is less than the typical force exerted by these spring latch.
The dead latch plunger is also configured as a flat plate that is oriented in a plane that extends longitudinally relative to the longitudinal throw direction so as to have a leading edge. The strike elements are then supported on the flat plate and extend laterally thereof. Each of the strike elements is configured as face with an elongated finger projecting therefrom, and each of these fingers extend transversely to the longitudinal throw direction and transversely to the plane of the flat plate. The adjustably and selectively mounted shield is then interposed between the fingers and the head portion. Here, also, the flat plate of the dead latch plunger has a dovetail channel formed therein and the base of each strike element includes a dovetail projection received in the groove for sliding movement therein.
The drive preferably includes a motor operative to rotatably drive a crank with the crank operative to reciprocate both the spring latch plunger and the dead latch plunger. Moreover, the crank operates to first drive the dead latch plunger from the advance position to the withdrawn position and next drive the spring latch plunger from the retracted position to the extended position. The crank can be a rotatable member that is operative to continuously drive the dead latch plunger between the advance and the withdrawn positions during a rotary cycle thereof.
The present invention also concerns a method of actuating a mortise-type latch bolt assembly of the type described above. Broadly, the method includes the first step of placing an attack head within a cavity having an opening in the jam of the door. The attack head is placed at a position to engage the spring latch of a mortise-type latch bolt assembly when the door is in a fastened state with this attack head being in a retracted position. Next, a plurality of independent strike elements are configured within the cavity opening so as to form a strike surface for engaging the dead latch bolt pin when the door is in the fastened state. Here, the strike surface has an advanced position when the dead latch bolt pin is in the disabled position when the door is in the fastened state. Next, the method includes the step of withdrawing the strike surface to a withdrawn position so as to allow the dead latch bolt pin to move into the enable position. Next, the attack head is moved from the retracted position to an extended position thereby to move the spring latch to the release position and disengage the spring latch from the cavity within the door jam. Thereafter, the attack head is retracted to the retracted position.
This general method can also include the step of moving the strike surface from the withdrawn position to the advanced position when the attack head is moved from the retracted position to the extended position. The step of configuring the strike elements can be accomplished wherein the strike surface and the attack head substantially block the opening to the cavity within the door jam. The method of configuring the strike surface can include placing of the strike elements on opposite sides of the attack head. Finally, the method according to the general invention can include the cyclical driving of the attack head in the strike surface after they have been placed in the jam of the door and configured according to the first two steps of the general method.
These and other objects of the present invention will become more readily appreciated and understood from a consideration of the following detailed description of the exemplary embodiment of the present invention when taken together with the accompanying drawings, in which: